Magnetic valves normally comprise an armature tube accommodating a movable armature being made from a soft magnetic material, i.e. a material which becomes magnetic when subjected to a magnetic field, e.g. provided by a coil being energized. A coil is arranged around the armature in such a manner, that when the coil is energized, i.e. an electrical current is supplied to the windings of the coil, a magnetic field is induced in the armature, causing the armature to move along an axial direction inside the armature tube.
Magnetic valves further comprise a valve housing accommodating a valve seat and a valve closing element being movable between a position in which it abuts the valve seat and positions in which it does not abut the valve seat. The valve closing element is connected to the armature in such a manner that movements of the armature, due to energizing or de-energizing the coil, causes movements of the valve closing element between abutting and non-abutting positions. When the valve closing element is not arranged in abutment with the valve seat, the valve is open and a flow of fluid through the valve from an inlet opening to an outlet opening is allowed. When the valve closing element is arranged in abutment with the valve seat, the valve is closed and a flow of fluid through the valve is prevented. Thus, the valve can be opened and closed by controlling a supply of electrical current to the coil.
Normally, it is desirable to make the armature tube as thin as possible in order to ensure that the magnetic flux induced by the coil is efficiently conveyed to the armature top. Furthermore, the armature tube must be wear resistant and have a high yield strength, in spite of the low material thickness, in order to ensure that it can resist wear originating, e.g., from the movements of the armature inside the armature tube, and in order to ensure that the armature is capable of withstanding the pressure levels which are anticipated inside the armature tube. To this end, the armature is often made from a hard and wear resistant material, such as austenitic stainless steel, e.g. cold worked austenitic stainless steel.
The valve housing, on the other hand, is normally made from a material which is cheap and which can easily be processed, e.g. brass. Furthermore, the material selected for the valve housing should be compatible with the fluid which is flowing through the valve, e.g. a refrigerant.
U.S. Pat. No. 6,268,784 discloses a magnetic valve for liquid and gaseous working media. The valve includes a first cylindrical housing part that is encompassed on its outside by a magnetic coil and has a cylindrical recess inside which extends in an axial direction to accommodate and guide an armature. A second cylindrical housing part is arranged coaxially to the first housing part and includes a cylindrical recess extending in an axial direction, the said recess being in connection to outside valve ports and in which a valve seat cooperating with a tappet is arranged. The first and second housing parts form a housing which is made in one piece of a ferromagnetic material.
DE 101 30 629 discloses a valve assembly for a magnetic valve, the valve assembly comprising a housing, a valve element with an armature, which is arranged in the housing, a valve seat, and a coil.
U.S. Pat. No. 7,044,111 discloses a purge valve including an actuator, a valve body, and a valve closure member disposed in the valve body. The actuator is disposed along a longitudinal axis, and includes an electromagnetic coil having a hollow core extending along the longitudinal axis, a stator disposed in the hollow core, and a permanent magnet armature disposed proximate the stator. The valve body is disposed proximate the actuator, and defines a flow passage extending along the longitudinal axis.